A Life Cycle Assessment of Silica Sand: Comparing the Beneficiation Processes

Silica sand or quartz sand is mineral resource with wide varieties of applications (glass industry, construction and steel industry etc.) Republic of Croatia has confirmed reserves of 40 million tons and long tradition of exploitation and processing. In recent years silica sand exploitation was performed with lower capacity of 75 thousand tons per year. In this article environmental profiles of different processing options are calculated, and included into cradle to gate life cycle study of glass grade silica sand. Key segments of production process are identified and ranked and a criterion for choice of technology at design level is given. In this research eight variations of silica sand production process are designed. For the purpose of design, equipment and machinery database is generated. Designed normative in production processes are checked for consistency with field data. Life cycle assessment is performed using Sima Pro software. For life cycle impact assessment ReCiPe method is chosen. Analyzed alternatives had in common surface excavation using bulldozers ; transportation from excavation site to processing plant (3 km) using dumpers ; washing and sizing. Variants were distincted by following processes: Alternative 1: drying ; electrostatic separation of feldspar, magnetic separation of magnetic minerals ; road transport of dried silica sand (water content less than 1% mass) using lorry (truck) on transporting distance 100 km. Alternative 2-1: road transport of wet silica sand (water content 6% mass) using lorry (truck) on transporting distance 100 km ; drying in glass plant using waste heat. Alternative 2-2 included drying ; road transport of dried silica sand (water content less than 1% mass) using lorry (truck) on transporting distance 100 km. Alternative 3-1: flotation of mica, heavy minerals and feldspar ; road transport of wet silica sand (water content 6% mass) using lorry (truck) on transporting distance 100 km ; drying in glass plant using waste heat. Alternative 3-2 included drying ; road transport of dried silica sand (water content less than 1% mass) using lorry (truck) on transporting distance 100 km. Alternative 4-1: gravitation concentration of quartz ; road transport of wet silica sand (water content 6% mass) using lorry (truck) on transporting distance 100 km ; drying in glass plant using waste heat. Alternative 4- 2 included drying ; road transport of dried silica sand (water content less than 1% mass) using lorry (truck) on transporting distance 100 km. Alternative 5 was created using only EcoInvent database to represent the silica sand imported by railroad transport on distance 700 km